A sodium-led bicarbonate spring — the classic 'jūsō-sen' style, soft and rounded on the skin. Hypotonic, neutral pH, sitting in the Japanese 'beauty-water' family. Metasilicic acid runs to 108.6 mg/kg, leaving a thin silica film that makes skin feel smoother afterwards. Free CO₂ at 284 mg/kg arrives as an aromatic gas, paired with a faint mineral tang and the merest whisper of H₂S at the wellhead.
Good for
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
- 病気の活動期(特に熱のあるとき)、活動性の結核、進行した悪性腫瘍又は高度の貧血など身体衰弱の著しい場合、少し動くと息をはずませるような重い心臓又は肺の病気、むくみのあるような重い腎臓の病気、消化管出血、目に見える出血があるとき、慢性の病気の急性憎悪期
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺245mgP57 national85%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺14.7mgP32 national6%
- Magnesiummild; a laxative if you drink itMg²⁺7.6mgP58 national5%
- Potassiumminor; matters for drinking limitsK⁺13.8mgP52 national3%
- AmmoniumNH₄⁺0.80mgP61 national0.3%
- LithiumLi⁺0.20mgP40 national0.2%
- BariumBa²⁺1.1mgP90 national0.2%
- AluminumAl³⁺0.10mgP54 national0.1%
- StrontiumSr²⁺0.50mgP68 national0.1%
- ManganeseMn²⁺0.20mgP45 national0.1%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻635mgP81 national82%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻71.8mgP33 national16%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻8.1mgP19 national1%
- FluorideF⁻0.20mgP17 national0.1%
- Iodideyellows in air; helps blood lipidsI⁻0.10mgP37 national
- Hydrogen phosphateHPO₄²⁻0.05mgP22 national
- Thiosulfateoxidized sulfurS₂O₃²⁻0.03mgP32 national
- Bromidetrace, sea-originBr⁻0.0040mgP7 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃109mgP58 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂12.9mgP62 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂284mgP92 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.04mgP53 national
- CadmiumCd< —mg
- ChromiumCr< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- 筋肉若しくは関節の慢性的な痛み又はこわばり(関節リウマチ、変形性関節症、腰痛症、神経痛、五十肩、打撲、捻挫などの慢性期)、運動麻痺における筋肉のこわばり、冷え性、末梢循環障害、胃腸機能の低下(胃にガスがたまるなど)、軽症高血圧、耐糖能異常(糖尿病)、軽い高コレステロール血症、軽い喘息又は肺気腫、自律神経不安定症、ストレスによる諸症状(睡眠障害、うつ状態など)、病後回復期、疲労回復、健康増進
- きりきず、末梢循環障害、冷え性、皮膚乾燥症
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.